This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Degradation of protein crystals by X-ray beams is an important factor in the design of an X-ray crystallography experiment. Despite the fact that researchers have been using cryogenic temperatures to mitigate radiation damage for over 20 years, the underlying mechanisms involved are still the subject of debate. In this round of experiments, we intend to isolate the contribution to radiation damage that comes from the presence of a heavy atom. By looking at the way radiation damage is manifested in the structure just above and below the zinc edge in zinc-containing insulin crystals, we will be able to determine the effect of e.g. Auger electrons from the zinc core-hole.